Gel compositions

ABSTRACT

The invention relates to a composition which comprises a dispersion of micro spheres in a gel comprising an oily base and an organic polymeric gelling agent.

[0001] This invention relates to gel compositions for filling cables,such as communication cables, in particular to gel compositionscontaining micro spheres, and to methods of preparing such gels.

BACKGROUND OF THE INVENTION

[0002] Communications cables typically comprise a signal-conducting coresurrounded by a protective sheath. The core can, for example, conductlight signals or electrical signals. In many cables the space betweenthe conductor and sheath contains a filler, the role of which is toprotect and cushion the core from external forces that might be producedby, for example, bending or coiling, particularly in the case offibre-optic cables. A further role of the filler is the prevention ofwater ingress which is particularly pertinent should the core comprise ametal such as copper. In order to fulfil these requirements, the fillermust display a number of characteristics. The filler must be ofsufficient viscosity in order to allow lateral movement of the corewhich occurs during, for example, bending, coiling or laying. Theviscosity must however not be so low as to allow a drip wise loss offiller during vertical laying of cables. Moreover, this balance ofproperties must be maintained over a temperature range of −40 to +80° C.The filler must be formulated to be chemically compatible with cablegrade polymers, which includes not only the cable sheath but alsocoatings typically found on optical fibres. The filler should also showa high degree of elasticity in order to absorb the force of impacts thatthe cable sheath may undergo during its operating lifetime. Relativelyhigh ambient temperatures can be reached through fabrication of suchcables resulting in thermal expansion of the filler which then leads tothe formation of holes and cavities on cooling. Such holes and cavitiescan potentially become a water path which in fibre optic cables can leadto attenuation of the light wave guide. Thus cable fillers shouldideally show low thermal conductivity. For electrical applications orcores transmitting electrical signals, it is advantageous if the fillerhas a low permitivity thus insulating the conducting core. This has theadditional benefit of rendering the filler hydrophobic therebyprotecting the core from water ingress. The anti-drip resistance offillers can be improved by reducing their specific weight. Finally, foreasy handling, it is preferred if the filler is semi-dry to the touch,rather than sticky.

[0003] Existing fillers used in telecommunication cables include oilgels which are primarily blends of oils and gelling agents. Inapplication, they penetrate between bundles of for example, denselypacked insulated copper conductors and in so doing insulate them frommoisture. The oil, which comprises a major part of the blend, can be anaphthenic or paraffinic processing oil, a mineral oil, a syntheticproduct such as a polybutane or a silicone oil. Gelling agents includewaxes, silicic (silica gels) acids, fumed silica, fatty acid soaps andthermoplastic elastomers. Typically the gelling agent comprises lessthan 10% of the whole.

[0004] One particular family of thermoplastic elastomers marketed underthe trade mark ‘Kraton’ (Shell Chemical Company), comprises di-block,tri-block or multi-atm molecular configurations of rubber andpolystyrene segments.

[0005] U.S. Pat. No. 5,657,410 describes an optical transmission elementwhich includes a filler comprising between 80% and 95% by weight of amonomeric plasticizer having a molecular weight in the range 200-2000grams per mole. Such monomeric plasticizers include esters ofphthalates, trimellitates, phosphates and fatty esters. Additionalsubstances may also be added such as thickeners. The thickener can takethe form of small spheres. Hollow spheres are preferred due to theirgreat compressibility and easy processibility. Thixotropic agents mayalso advantageously be added. They include finely divided or fumedsilica, alumina, and bentonites as well as mixtures of these substances.

[0006] The use of micro spheres, e.g. hollow micro spheres, in cablefilling compounds is also described in U.S. Pat. No. 5,698,615. In thisdisclosure the cable filler comprises a substantially dry hydrophiliccomposition containing inter alia, in addition to the micro spheres,water absorbent swellable powder particles, preferably of particle sizerange 1-30 μm and a “parting powder” having particles of preferably{fraction (1/100)}th the size of the swellable powder particles. Due tothe hydrophilic nature of the swellable powder particles, thecomposition always retains some water. The parting powder particles aredisposed between the swellable powder particles to prevent agglomerationas the swellable polymer particles absorb water. Suitable swellablepowder particles are those based on the polyacrylic acid sodium salt.The parting powder particles are typically inorganic powders such astalcum, mica, graphite and silicates. The absorption of water by theswellable powder particles transforms the dry composition into a gelwhich seals the core from further water ingress. The compositions canalso contain a small amount of an oil or an adhesive to reduce anypotential dust hazard.

[0007] WO 99/15582 discloses a composition which includes expandablehollow micro spheres for use in encapsulation of for examplesemi-conductor chips. Such hollow micro spheres, similar in morphologyto the micro spheres disclosed in U.S. Pat. No. 5,657,410 and U.S. Pat.No. 5,698,615, comprise a polymeric shell encapsulating a blowing agent.When heated, the polymeric shell of the expandable micro spheresgradually softens and the liquid blowing agent, typically isobutane,starts to evaporate thus expanding the microsphere.

[0008] A light wave guide lead is disclosed in U.S. Pat. No. 5,335,302which comprises at least one light wave guide accommodated in aprotective sheath and embedded in a pasty filling material containingsmall micro spheres. The small micro spheres, which can be solid andrigid, solid and elastic or hollow and elastic, are included as fillersto reduce the cost, and to provide improved rheological and cushioningproperties. A preferred filler comprises an oil, a thixotropic agent(for example fumed silica) and an unspecified organic thickener.

SUMMARY OF THE INVENTION

[0009] In one aspect, the present invention provides a composition,particularly a composition suitable for use as a cable filler, whichcomprises a dispersion of micro spheres in a gel comprising an oily baseand an organic polymeric gelling agent.

[0010] In another aspect, the invention provides a composition,particularly a composition suitable for use as a cable filler, whichcomprises a dispersion of micro spheres in a gel comprising an oily baseand an organic polymeric gelling agent, the composition containingsubstantially no thixotropic agent other than the organic polymericgelling agent.

[0011] In a further aspect, the invention provides a composition,particularly a composition suitable for use as a cable filler, whichcomprises a dispersion of micro spheres in a gel comprising an oily baseand a polymeric gelling agent wherein the polymeric gelling agentcomprises, consists essentially of, or consists of a thermoplasticelastomer.

[0012] Another aspect of the invention provides a composition,particularly a composition suitable for use as a cable filler, whichcomprises a dispersion of micro spheres in a gel comprising an oily baseand a polymeric gelling agent wherein the polymeric gelling agentcomprises, consists essentially of, or consists of a thermoplasticelastomer other than polystyrene-isoprene rubber.

[0013] Yet another aspect of the invention provides a composition,particularly a composition suitable for use as a cable filler, whichcomprises a dispersion of micro spheres in a gel comprising an oily baseand a polymeric gelling agent wherein the polymeric gelling agentcomprises, consists essentially of, or consists of a thermoplasticelastomer, excluding compositions containing polystyrene-isoprene rubberand an organic thickener.

[0014] A further aspect of the invention provides a composition,particularly a composition suitable for use as a cable filler, whichcomprises a dispersion of micro spheres in a gel comprising an oily baseand a thermoplastic elastomer as a gelling agent, the compositioncontaining substantially no thixotropic agent in addition to thethermoplastic elastomer.

[0015] Another aspect of the present invention is a gel compositioncomprising a dispersion of organic microspheres in a gel comprising anoily base and a thermoplastic elastomer, the gel containingsubstantially no thixotropic agent in addition to the thennoplasticelastomer and being substantially free from silica, for example fumedsilica. In the context of the present invention, the term “substantiallyno thixotropic agent other than the organic polymeric gelling agent”means that the composition contains less than 5% of a thixotropic agentother than the organic polymeric gelling agent, preferably less than 1%and more preferably, less than 0.2%, and the term “substantially freefrom silica” means that the composition contains less than 3% silica,preferably less than 1% and more preferably, less than 0.1%.

[0016] A particular embodiment of the invention is a composition,particularly a composition suitable for use as a cable filler, whichcomprises a dispersion of micro spheres in a gel comprising an oily baseand an organic polymeric gelling agent wherein the gel is substantiallyfree of fumed silica.

[0017] The gels of the invention may additionally contain ananti-oxidant.

[0018] The oily base can comprise a hydrocarbon oil or a silicone oil.Particularly preferred hydrocarbon oils include white mineral oils andpoly(α-olefin) synthetic oils. The oily base typically constitutes 1-99%by weight of the gel, more preferably 5-99% by weight of the gel, inparticular 80-99% by weight of the gel.

[0019] Examples of thermoplastic elastomers include thermoplasticrubbers. The thermoplastic elastomer can be a copolymer, for example ablock copolymer processing a di-block, a tri-block, or a multi-armmolecular configuration. In one particular embodiment, the blocks arecomprised of either rubber or polystyrene. The rubber can be saturatedolefin rubber composed of ethylene, propylene or butylenes monomerunits. Alternatively, the rubber can be an unsaturated olefin rubbercomprising butadiene or isoprene monomer units.

[0020] Particular examples of thermoplastic elastomers includestyrene-ethylene/butylene styrene tri-block copolymer (SEBS),styrene-ethylene/propylene di-block copolymer (SEP), ethylene/propylenemulti-arm copolymer (EP), styrene-butadiene-styrene tri-block copolymer(SBS) and styrene-isoprene-styrene tri-block copolymer (SIS).

[0021] Commercially available thermoplastic elastomers include thecopolymers available under the trade mark “Kraton” from Shell.

[0022] The polymeric gelling agent is typically used in proportions inthe range 1-10% by weight of the composition more preferably, in therange 2-9% by weight of the composition, in particular in the range 3-8%by weight of the composition.

[0023] The micro spheres can be for example, solid rigid micro spheres,solid elastic micro spheres or compressible hollow micro spheres. Solidrigid micro spheres can be formed from a thermosetting resin such asmelamine-formaldehyde resin which has a relatively low thermal expansioncoefficient and in use would tend to lower the overall expansioncoefficient of the gel. This is particularly advantageous where the gelmay be heated during manufacture of, for example, fibre optic leads.During such processes, conventional materials tend to expand when heatedleaving holes or cavities around the wave guides on cooling. The holesor cavities can, under certain conditions, lead to an increase inattenuation of the light wave guides. The melamine-formaldehyde microspheres, available from Ubitek Company of Uchte, preferably have adiameter of <10 μm, in particular <1 μm.

[0024] Examples of solid elastic micro spheres are those comprisingpolyisoprene. The polyisoprene is not only elastic in its own right butcan additionally absorb considerable quantities of the oily base therebybecoming even more elastic. The mean diameter of the micro spheres ispreferably <10 μm, more preferably <1 μm.

[0025] One preferred embodiment of the invention uses compressiblehollow micro spheres each comprising a polymeric shell encapsulating ablowing agent. The polymeric shell is generally formed from a copolymer,for example a copolymer of vinylidene chloride and acrylonitrile. Theblowing agent can, for example, be isobutane or isopentane. In addition,the micro spheres can be expanded or unexpanded. The polymeric shell ofthe unexpanded micro spheres softens on heating, so allowing theevaporating blowing agent to expand the volume of the micro spheres.

[0026] Such hollow micro spheres whether expanded or initiallyunexpanded, display a high degree of elasticity and additionally have alow specific weight. Use of such micro spheres in the gels disclosed inthis invention is advantageous in that they lower the overall specificweight of the gels and thus reduce or eliminate drip-out during verticallaying of the cable.

[0027] The hollow nature of the micro spheres means that the proportionof solid material is very low relative to the volume. Thus theiraddition to the gels of the invention leads to a reduction in theoverall thermal conductivity and a reduced likelihood of decompositionof any of the components of the gel or the creation of voids under theelevated temperatures reached during cable manufacture. The superiorelastic properties of the hollow micro spheres over their solidcounterparts gives improved protection to, for example, light waveguides during conveying, coiling or laying. Additionally, the problem ofattenuation of light waveguides due to the presence of holes or cavitieswithin the cable filling is also reduced as any increase in volume ofthe bulk of the filler due to heating during cable manufacture ismatched by a converse reduction in the volume of the hollow microspheres. Due to the compressible nature of such hollow micro spheres,their typical diameters are greater than those of their solidcounterparts. In fibre optic cable applications, diameters in the rangeof the diameter of the light wave guide can be used. For expanded hollowmicro spheres, the diameters will typically lie in the range 1-200 μm,more usually less than 100 μm, typically less than 75 μm, for example 15to 55 μm. For unexpanded hollow micro spheres, the mean diameter priorto expansion is typically in the range up to 50 μm, more usually lessthan 30 μm, for example in the range 10 to 20 μm.

[0028] The volume proportion of the micro spheres generally differs forsolid and hollow counterparts. The solid micro spheres are typicallyemployed in the volume range 1-50% by volume of the gel (v/v), morepreferably in the range 5-50% v/v. Where hollow micro spheres are used,they are typically present in the range 1-95% v/v, more preferably 5-95%v/v, in particular 50-95% v/v, the foregoing figures to the expandedvolumes.

[0029] The anti-oxidant can be selected from those commonly used in theart Phenolic anti-oxidants are preferred. The anti-oxidant is typicallypresent in an amount 0.01-1% w/w, for example 0.1-1% w/w.

[0030] In a further aspect, the invention provides a composition ashereinbefore defined for use as a cable filler.

[0031] In another aspect, the invention provides a cable, such as acommunications cable, containing a filler as hereinbefore defined.

[0032] In a still further aspect, the invention provides a cablecomprising a conducting core surrounded by a sheath, a composition ashereinbefore defined being disposed between the conducting core and thesheath. The conducting core can be, for example, an electrical conductoror a light conductor. The electrical conductor can be, for example, aconductor for conducting electrical signals such as telephone signals.

[0033] In a further aspect, the invention provides a process for makinga cable comprising a conducting core and a sheath, the processcomprising the step of extruding the cable sheath onto the conductingcore and interposing a composition as hereinbefore defined between theconducting core and sheath during the extrusion step.

[0034] In another aspect, the invention provides a process for preparinga gel as hereinbefore defined; the process comprising:

[0035] (a) heating the oily base to a temperature in the range 110° C.to 120° C.;

[0036] (b) adding the polymeric gelling agent to the oily base andblending to form a mixture;

[0037] (c) cooling the mixture to a temperature of less than 90° C.;

[0038] (d) adding and blending in the micro spheres; and optionally

[0039] (e) adding and blending in an anti-oxidant: and/or

[0040] (f) maintaining the mixture under vacuum to remove entrapped gas.

[0041] In a preferred embodiment, the process comprises:

[0042] (i) blending at least one oil in a heating-blending tank;

[0043] (ii) heating the blended oils to 110-120° C. in a stirredheating-blending tank;

[0044] (iii) adding and blending the polymeric gelling agent to the oilybase under high shear for no more than one hour after of the oily baseto a blending-cooling tank, allowing the temperature of the blend torise to more than 120-130° C.;

[0045] (iv) cooling the blend to <90° C. and transferring to a stirredmain reactor,

[0046] (v) adding and blending an antioxidant;

[0047] (vi) adding and blending the micro spheres, drawn to the reactorunder vacuum or pumping, for at least two minutes;

[0048] (vii) maintaining the vacuum for at least another 10 minutes inorder to effect removal of air bubbles prior to release of the finishedgel.

[0049] Although the temperature of the mixture is typically <90° C.after cooling, more preferably it is <80° C., in particular it is <70°C.

[0050] Further and particular aspects of the invention are as set out inthe claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The invention will now be illustrated, but not limited, byreference to the particular embodiments shown in the accompanyingdrawings, in which:

[0052]FIG. 1 shows a cross-sectional view of an electrical cable; and

[0053]FIG. 2 shows a cross-sectional view of an optical cable;

[0054]FIG. 3 is a graph of viscosity against shear rate for thecomposition of Example 1 at 25° C.; and

[0055]FIG. 4 is a graph of viscosity against shear rate for thecomposition of Example 2 at 25° C.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0056]FIG. 1 shows a cross-sectional view of an electrical cable 11,comprising, in this example, four electrical leads 13 encased incladding 12. The electrical leads 13 themselves comprise an electricalconductor 14, preferably of copper, and an outer insulation 15,typically of polyethylene. Interspersed between the electrical leads 13and the outer cladding 12, is a filler gel composition 16. In thisembodiment, the filler composition can comprise an oily base, athermoplastic rubber as polymeric gelling agent and micro spheresdispersed therein and optionally an anti-oxidant. The electrical cable,typically comprising a copper core, can be used for the purposes oftelecommunications or distribution of electricity.

[0057] Although FIG. 1 shows a cross-sectional view of an electricalcable comprising four conductors in a star quad configuration, it willbe appreciated that cables having a variety of different configurationscan be used as alternatives to the configuration shown.

[0058]FIG. 2 shows an optical cable 21 comprising three optical fibrebuffer tubes 23 encased in cladding 22. The optical fibre buffer tubes23 themselves consist of an optical fibre 24 provided with a protectivecoating 26 and a protective sheath 25. The filler composition 27 isdisposed between the coated optical fibre and the protective sheath.Additionally, it fills the interstices formed between individual buffertubes and between the buffer tubes and the internal surface of the cablecladding.

[0059] Examples of specific gels suitable for use in cables, such as thecables illustrated in FIGS. 1 and 2 are as follows:

EXAMPLE 1

[0060] A gel filler was prepared having the following composition:Component Concentration (% wt.) White mineral oil 89.0 SN 500 (Mobil)Thermoplastic elastomer 5.5 Kraton 1701 or 1702 (Shell) Micro spheres(pre-expanded) 5.0 Expancel 091 DE (Triones Chems. Int.) Anti-oxidant0.5 Irganox L 135 (Ciba-Geigy)

[0061] The gel filler of this example is suitable for filling theinterstices between the tubes and conductors (flooding) and is not indirect contact with the fibre guides.

[0062] The gel was prepared as follows:

[0063] The oily base was introduced into a stirred heating-blending tankand heated to 110-120° C. before transferring to a high shearblending-cooling tank, whereupon the thermoplastic elastomer (Kraton)(in the form of granules) was added. The mixture was blended under highshear conditions using a multi-purpose immersion type mixer emulsifier(Silverson Machines Limited, Model GDD 25) for no more than 60 minutes.During the blending process, the temperature of the mixture was allowedto rise to 120-130° C. The mixture was cooled by means of a cold waterchiller system, and the chilled mixture was transferred to a stirredmain reactor where the anti-oxidant was added. A vacuum was then createdinside the reactor in order to suck in the micro spheres which weremixed into the blend over a period of at least two minutes. The vacuumwas maintained for at least a further ten minutes in order to effectremoval of any air bubbles. The vacuum was then released, the stirrerswitched off and samples taken prior to release of the finished gel fromthe main reactor.

[0064] The product was characterised by a number of tests, the resultsof which are summarised in Table 1 below. The thermal conductivitiesreferred to in the table were determined as follows:

[0065] Specimen discs were created by scooping the gels into a pair ofnylon rings of mean internal diameter 70.1 mm and mean thickness 10.03mm and placing cling film above and below. A small correction was madeto allow for the extra interface introduced by the cling film. Thethermal conductivity of the specimens was measured using a 76 mm guardedhotplate. A pair of specimen discs were mounted, under the pressure oftwo cooled plates, on either side of a guarded heater plate. The cooledplates were maintained at a constant temperature to better than ±0.05°C. The surfaces of the plates had emittances of better than 0.9. Thetemperature of the annular guard on the heater plate was matched to thatof the central part to better than ±0.01° C. in order to minimiselateral heat flow in the specimens. The heater plate and the specimenswere insulated with a glass fibre blanket to further reduce edge heatlosses. The temperature drop through the specimens was fixed at 14° C.and about 5 hours was allowed for thermal equilibrium to be establishedbefore final readings were taken.

[0066] The aging test was derived from YD/T839.4-1996 (PRC Method)except that the temperature and duration of the test was altered. TABLE1 Physical Properties Property Value Test Method Density (20° C.) g/ml0.356 ASTM D 1475 Viscosity (100 s^(.1), 25° C.) Pa · s 23.63 HaakeVT500 Tube drainage (7 mm id/80° C./24 hrs.) Pass EIA/TIA-455-81A ConePenetration (23° C.) dmm 335 ASTM D937 Cone Penetration (−30° C.) dmm167 ASTM D937 Cone Penetration (−40° C.) dmm 120 ASTM D937 Oilseparation (80° C./24 hrs.) % wt. 0 FTM791 (321) Volatile loss (80°C./24 hrs.) % w/w 0.17 FTM791 (321) OIT (190° C.) min. 34.75 ASTM D3895Thermal conductivity (23° C.) W/m · K 0.077 see above Thermalconductivity (80° C.) W/m · K 0.078 see above Hydrogen generation (80°C./24 hrs.) μl/g 0.010 Acid Value mgKOH/g 0.036 BS2000 Aging (100°C./240 hrs.) Pass see above UV exposure (25° C./14 days) PassTemperature exposure (240° C./5 mins.) Pass

[0067] Table 1 shows that the density of the gel is low whichcontributed to good anti-drip properties (measured at 80° C.). Lowtemperature performance was assessed by cone penetration at −40° C.whilst high temperature performance was tested by a combination of thedrip test, oil separation and volatile loss tests all carried out at 80°C. and the oxidative induction time test carried out at 190° C. Anoxidative induction time in excess of 20 minutes is desirable. Theresults indicate that the gel has a working temperature range of −40 to+80° C. Furthermore the rheological behaviour of the gel, shown in FIG.3, is thixotropic (shear thinning) allowing for cold pumping andprocessing, and thus cable filling in the absence of voids created bygel shrinkage.

[0068] Thermal conductivity was determined at 23° C. and 80° C. Thevalues for the conductivity were low reflecting the low density of thegel, and varied little with temperature suggesting a material possessinga disordered structure. The good insulating properties indicated amaterial possessing good resistance to thermal decomposition that canoccur at the elevated temperatures reached during cable manufacture. Inaddition, the gel would be less sensitive to the thermal expansion andcontraction that can take place during cable manufacture leading to theformation of voids in the cable filling. For purposes of comparison, thethermal conductivities of a range of materials are given in Table 2.TABLE 2 Thermal Conductivities of Various Materials Material Thermalconductivity W/m · K Comment Aluminium 200 Very good conductor Water 0.6Olive oil 0.17 Paraffin 0.15 Air 0.024 Very good insulator

[0069] The gel showed good aging properties and uv and temperatureresistance. There was also low hydrogen gas generation.

EXAMPLE 2

[0070] A similar gel filler was prepared in a similar manner to thatdescribed in Example 1 but with a different grade of mineral oil. Thegel was suitable for use in small pair telephone copper cable fillingand flooding applications.

[0071] The gel was subject to a number of physical tests. The results ofthe physical tests were similar to those of the composition of Example 1and therefore only the electrical properties are quoted in Table 3.TABLE 3 Physical Properties Property Value Test Method Dielectricconstant (23° C.) 1.62 ASTM D924 Dielectric dissipation factor (1 MHz)4.4 × 10⁻⁴ ASTM D924 Volume resistivity (23° C.) Ohm · cm 2.8 × 10¹⁵ASTM D257 Break down voltage kV 86

[0072] The gel is characterised by a low relative permitivity (1.62) anda high volume resistivity (2.8×10¹⁵ Ohm.cm). For purposes of comparison,the relative permitivities of a number of materials are given in Table4. TABLE 4 Relative Permitivities of Various Materials Material Relativepermitivity Air (normal pressure) 1.0005 Paraffin wax 2 Paraffin oil 4.7Glass 5-10 Mica 6 Methyl alcohol 32 Water 81

EXAMPLE 3

[0073] A gel suitable for use in filling loose tubes and interstitialfilling between ribbons and open slotted cores, was prepared in asimilar manner to that described in example 1. The formula for this gelis set out below: Component Concentration (% wt.) Poly α-olefin oil^(a)66.37 Durasyn 166 (Amoco) White mineral oil 22.13 Whiterex 250 (BP/MobilThermoplastic elastomer 7.5 Kraton 1701 or 1702 (Shell) Micro spheres(pre-expanded) 3.5 Expancel 091 DE (Triones Chems. Int.) Anti-oxidant0.5 Irganox L 135 (Ciba-Geigy)

[0074] The gel was subject to a number of physical tests. The results ofthe physical tests, which were similar to the results of the compositionof Example 1, are shown in Table 5.

[0075] In addition the tensile strength and coating strip force ofoptical fibres were tested according to the standards FOTP-28 andFOTP-178 respectively. The optical fibre was CPC6 manufactured bySiecor. The tests were carried out after ageing of the fibres in forcedair chambers for 30 days at 85±1° C. whilst immersed in the gel.Measurements were carried out at 20° C. and 70% relative humidity. Thetensile strength was measured on thirty 0.5 mm samples from fourdifferent groups at a rate of elongation of 500±50 mm/min. 50 mm sampleswere used for the coating strip force tests using a stripping tool at aspeed of 500±50 mm/min. Average tensile strength and coating strip forcevalues for a control sample were 68.89 N and 3.61 N respectively. TABLE5 Physical Properties Property Value Test Method Density (20° C.) g/ml0.438 ASTM D 1475 Viscosity (200 s^(.1), 25° C.) Pa · s 7.95 Haake VT500Tube drainage (7 mm id/80° C./24 hrs.) Pass EIA/TIA-455-81A ConePenetration (23° C.) dmm 396 ASTM D937 Cone Penetration (−40° C.) dmm250 ASTM D937 Oil separation (80° C./24 hrs.) % wt. 0 FTM791 (321)Volatile loss (80° C./24 hrs.) % w/w 0.06 FTM791 (321) OIT (190° C.)min. 31.04 ASTM D3895 Thermal conductivity (23° C.) W/m · K 0.077 seeexample 1 Thermal conductivity (80° C.) W/m · K 0.078 see example 1Hydrogen generation (80° C./24 hrs.) 0.015 μl/g Relative permitivity (50Hz, 25° C.) 1.65 ASTM D150 Volume resistivity (23° C.) Ohm · cm 19 ×10¹⁴ ASTM D257 Tensile strength (20° C./70% RH) N 65.07 FOTP - 28Coating strip force (20° C./70% RH) N 3.88 FOTP - 178 Aging (100° C./240hrs.) Pass see example 1 UV exposure (25° C./14 days) Pass Temperatureexposure (240° C./5 mins.) Pass

[0076] The shear sensitive behaviour of the viscosity is illustrated inFIG. 4 and shows that the gel is thixotropic or shear thinning. This gelalthough of lower viscosity than the gel of example 1, still passed thedrainage test. The low temperature performance, chard by the conepenetration at −40° C., was exceptional. This is particularly importantas this gel is used in direct contact with optical fibres and mustmaintain flexibility at low temperatures to avoid applying stresses tothe aforementioned fibres or micro bending caused by contractio whichcan lead to an increase in attenuation. The tensile strength and coatingstrip force results suggested that there was no deterioration in themechanical strength of the fibres or degradation in the fibre coatingafter exposure to the gel.

EXAMPLE 4

[0077] This gel, formulated for filing loose tubes and interstitialfilling between ribbons and open slotted cores particularly for use withpolypropylene cable polymers, was prepared in a similar manner to thatdescribed in example 1. The formula for this gel is set out below:Component Concentration (% wt.) Silicone oil 94.7 F111/5000 (Ambersil)Fumed silica 1.8 M5 (Cabot) Micro spheres (pre-expanded) 3.0 Expancel091 DE (Triones Chems. Int.) Cross-linking additive 0.5

[0078] The resulting gel was subject to a number of physical andchemical tests, the results of which are summarised in Table 6 below.

[0079] The gel was tested for compatibility with polypropylene using thefollowing method:

[0080] Six 50 mm long samples of buffer loose tubes were weighed to0.00001 g. Five of the samples were subsequently immersed in the gel andall six aged in an air-circulated oven at 80° C. for two weeks. Thesamples were then re-weighed. TABLE 6 Physical Properties Property ValueTest Method Density (20° C.) g/ml 0.51 ASTM D 1475 Viscosity (100s^(.1), 25° C.) Pa · s 32.86 Haake VT500 Tube drainage (7 mm id/80°C./24 hrs.) Pass EIA/TIA-455-81A Cone Penetration (23° C.) dmm 340 ASTMD937 Cone Penetration (−40° C.) dmm 280 ASTM D937 Oil separation (80°C./24 hrs.) % wt. 4.97 FTM791 (321) Volatile loss (80° C./24 hrs.) % w/w0.11 FTM791 (321) OIT (190° C.) min. 33.15 ASTM D3895 Hydrogengeneration (80° C./24 hrs.) μl/g 0.012 Tensile strength (20° C./70% RH)N 66.00 FOTP - 28 Coating strip force (20° C./70% RH) N 4.10 FOTP - 178Aging (100° C./240 hrs.) Pass see example 1 UV exposure (25° C./14 days)Pass Temperature exposure (240° C./5 mins.) Pass Polypropylenecompatibility (80° C./ Pass see above 2 wks.)

[0081] The results from the low temperature cone penetration, and theoil separation, volatile loss and oxidative induction time experimentssuggest that the operating range of this gel is −40 to +80° C. Thetensile strength and coating strip force results suggested that therewas no deterioration in the mechanical strength of the fibres ordegradation in the fibre coating after exposure to the gel. The gel wasfound to be compatible with polypropylene as there was no weight gain inthe immersed tube samples after aging.

EXAMPLE 5

[0082] This gel, formulated for cable flooding and interstitial fillingapplications and is a swellable water blocking gel, was prepared in asimilar manner to that described in example 1. The formula for this gelis set out below: Component Concentration (% wt.) White mineral oil 89.5SN 500 (Mobil) Thermoplastic elastomer 4.0 Kraton 1701 or 1702 (ShellFumed silica 3.0 M5 (Cabot) Micro spheres (unexpanded) 2.5 Expancel 551DU (Triones Chems. Int.) Anti-oxidant 0.5 Irganox L135 (Ciba-Geigy)Monopropylene glycol 0.5 PGUSP-IS (Arco Chemical)

[0083] The gel was subject to a number of physical tests, the results ofwhich are summarised in Table 7 below. TABLE 7 Physical PropertiesProperty Value Test Method Density (20° C.) g/ml 0.87 ASTM D 1475Viscosity (200s^(.1), 25° C.) Pa.s 7.00 Haake VT500 Cable drainage (80°C./24 hrs.) Pass EIA/TIA-455-81A Cone Penetration (25° C.) dmm 340 ASTMD937 Oil separation (80° C./24 hrs.) % wt. 0 FTM791(321) OIT (190° C.)min. >40 ASTM D3895 Hydrogen generation (80° C./24 hrs) μl/g <0.02 AcidValue mgKOH/g <0.5 BS2000 Tensile strength (20° C./70% RH) N 66.00FOTP - 28 Coating strip force (20° C./70% RH) N 4.10 FOTP - 178

[0084] The presence of unexpanded hollow micro spheres in the gel meantthat the filler increased in volume by 1-10% on heating in thetemperature range 95-140° C. Such heat can originate from the extrusionhead during manufacture of, for example, fibre optic cables. Theswellable nature of the gel can help eliminate voids in the cablecreated on shrinkage of the cable filler and ensure a watertight sealaround the core. The elimination of voids also reduces the likelihood ofproblems of attenuation associated with fibre optic cables.

[0085] The gel can also be used for filling beneath the metalliclaminate where over-flooding with petroleum jelly type material canprevent scaling of the overlap whilst under-flooding may create a waterpath within the cable and lead to the problems of attenuation describedabove.

[0086] It will readily be apparent that numerous modifications andalterations can readily be made to the compositions exemplified in theExamples without departing from the principles underlying the inventionand all such modifications and alterations are intended to be embracedby this application.

1. A composition comprising a dispersion of micro spheres in a gelcomprising an oily base and an organic polymeric gelling agent, theorganic polymeric gelling agent comprising a thermoplastic elastomer;wherein the composition contains substantially no thixotropic agent inaddition to the thermoplastic elastomer.
 2. A composition according toclaim 1 wherein the organic polymeric gelling agent comprises athermoplastic elastomer other than polystyrene-isoprene rubber.
 3. Acomposition according to claim 2 wherein the organic polymeric gellingagent excludes compositions containing an organic thickener.
 4. Acomposition according to claim 1, the composition being substantiallyfree from silica.
 5. A composition according to claim 4, the compositionbeing substantially free from fumed silica.
 6. A composition accordingto claim 1, wherein the oily base comprises at least one oil selectedfrom naphthenic processing oil, paraffinic processing oil, mineral oil,synthetic oils and silicone oil.
 7. A composition according to claim 6,wherein the oily base comprises a poly(α-olefin) synthetic oil.
 8. Acomposition according to claim 1 wherein the oily base is present in anamount ranging from 1 to 99% by weight of the composition.
 9. Acomposition according to claim 1 wherein the oily base is present in anamount ranging from 50 to 99% by weight of the composition.
 10. Acomposition according to claim 1, wherein the oily base is present in anamount ranging from 80-99% by weight of the composition.
 11. Acomposition according to claim 1 wherein the organic polymeric gellingagent is a thermoplastic rubber.
 12. A composition according to claim 1wherein the organic polymeric gelling agent is present in an amount inthe range of 1-10% by weight of the composition.
 13. A compositionaccording to claim 1, wherein the organic polymeric gelling agent ispresent in an amount ranging from 2-9% by weight of the composition. 14.A composition according to claim 1, wherein the organic polymericgelling agent is present in an amount ranging from 3-8% by weight of thecomposition.
 15. A composition according to claim 1 containing one ormore anti-oxidants.
 16. A cable containing as a filler a compositionaccording to claim
 1. 17. A cable comprising a conducting coresurrounded by a sheath, a composition according to claim 1 beingdisposed between the conducting core and the sheath.
 18. A cableaccording to claim 16 wherein the conducting core is an electricalconductor or a light conductor.
 19. A process for making a cablecomprising a conducting core and a sheath, the process comprisingextruding the cable sheath onto the conducting core and interposing acomposition according to claim 1 between the conducting core and sheathduring the extrusion step.
 20. A process for preparing a compositionaccording to claim 1; the process comprising: a. heating the oily baseto a temperature in the range of 110° C. to 120° C.; b. adding theorganic polymeric gelling agent to the oily base and blending to form amixture; c. cooling the mixture to a temperature of less than 90° C.; d.adding and blending in the micro spheres; e. optionally adding andblending in an anti-oxidant; and f. optionally maintaining the mixtureunder vacuum to remove entrapped gas.
 21. A process for manufacturing acomposition according to claim 1 which process comprises: a. blending atleast one oil in a heating-blending tank, b. heating the blended oils to110-120° C., in a stirred heating-blending tank; c. adding and blendingthe organic polymeric gelling agent to the oily base under high shearfor no more than one hour after transfer of the oily base to ablending-cooling tank, allowing the temperature of the blend to rise tomore than 120-130° C.; d. cooling the blend to <90° C. and transferringto a stirred main reactor; e. adding and blending in an anti-oxidant; f.adding and blending the micro spheres, drawn to the reactor under vacuumor pumping, for at least two minutes; and g. maintaining vacuum for atleast another 10 minutes in order to effect removal of air bubbles priorto release of the finished composition.